The present invention relates to a method for firmly bonding a porous body and a fusion-made body utilizing the phenomenon of infiltration of a molten metal.
There are sometimes occasions in which firm bonding resistant to high temperatures is desired between a porous body such as a sintered metallic body prepared by the powder metallurgical process and a fusion-made body such as a body obtained by casting of a molten metal. Several methods are practiced for such a purpose of bonding including the pressure welding and diffusion bonding. The method of pressure welding is advantageous when the process is desired to be automatized but the method involves several drawbacks when eccentricity between the bodies to be bonded is great or the bodies to be bonded have very complicated configurations.
When the method of pressure welding is not applicable, the alternative method is the diffusion bonding owing to the absence of the limitation given by the configuration of the bodies to be bonded. The method of diffusion bonding is, however, sometimes defective because sufficient bonding strength is hardly obtained resulting in the breakage of the finished article at the interface between the bonded bodies in contrast to the very severe limitations in the working conditions such that, for example, the atmosphere must be evacuated to a high vacuum of, say, 10.sup.-4 Torr or better and the roughness of the surfaces under bonding must be well controlled.